Mass dissolving of quads into a single point
You can try to use the Decimate modifier, but to get clean topology, I am afraid you will have to do it manually, consider a complete retopology of your sculpture. If you decide to fix your mesh, you can speed up the merging process that batFINGER posted in the comments, by using Shift+R you can repeat the last action, thus reducing one step of the merging process. Which normally you will have to press Alt+M and then "Merge at Center", with this you only do it once, and next time it's just Shift+R.



The decimate modifier could get you some results quick, but you will have to keep an eye out for your topology, if you decide to use this method. Keep in mind that it may decimate already good topology you had. Also experiment with the three modes decimate has, "Collapse", "Un-Subdivide" and "Planar".